Wednesday, December 27, 2006

Forest Gardens


A forest garden is a garden that is modeled after a natural forest, and forest gardening is a new type of home landscaping for urban as well as rural areas. Forest gardens are very attractive, require little maintenance, and combine human and animal food production with ecology and conservation.

Forest gardens have a diverse collection of plants placed in multiple layers above deep mulching. The collection of plants produces flowers, food, and other products for human use. They live together along with insects and other animals that inhabit them, in an ecosystem in your yard.

The hobby of forest gardening was named by Robert Hart in Shropshire, England; but native peoples across the tropics have long created forest gardens. These "tropical home gardens" have includes a diversity of crops that are also arranged in multiple layers to mimic the structure and ecological conditions and functions of the surrounding local forests.

Robert Hart and others applied the same layering and mimicking principles to gardens modeled after deciduous forests in more temperate climates. These forest gardens work well in Ohio, because as much as 95% of Ohio was forestland originally, with numerous native plants that grow well. The same is true for other Midwest states.


Plants inhabit one or several layers in a naturally occurring forest and have a definite order of appearance. There are the high canopy trees, and underneath those, there is what is known as an understory (like a lower story) of shorter trees and pother lants. Under all the trees is a layer of saplings and shrubs, while under that layer, there is another layer of herbaceous plants.

Above the soil of the forest floor are the groundcovers. There are also vines that grow up through all the layers of the forest. The importance of planning a forest garden entails planning vertically. This includes the number of plants that can be stacked into layers in the available space (see suggestions below). A new garden area or landscape will require plans drawn roughly to scale by hand or on your computer. VISIO is a good program for that.

A good forest gardens can also live and grow around trees and shrubbery that already exists, or in part of a forest that is already standing. For small spaces, such as an urban yard, the canopy layer can be eliminated, and the design built around a shorter single tree, perhaps a fruit tree that will produce some food.

Plant layers in a naturally occurring forest do not grow uniformly across an area. Various species live on high slopes and others on flat ground. A forest's actual composition is much different at the edge of a clearing than the center of a wooded area. In a forest garden, we must consider the overall environment and match it with our intended uses of the space and particular plants.

If one corner of a forest garden is poorly drained, that corner should include plants that can tolerate wet roots. A forest garden can be installed to mimic the forest edges, with low growing species to the sunny side and taller plants to the back. Forest gardens can function to screen out an unpleasant view or cold winds. Deciduous forest gardens can shade a house in the summer and let the sun in to warm it in the winter season to increase home comfort and reduce utility bills. Appearances are also important. The art and architectural principles of plant grouping, balance, and harmonious design that are covered in basic landscape design books also apply to forest gardens.

Natural forests grow without human intervention and forest gardens eventually do the same. A sheet mulch keeps the plants moist without the need for much more watering, and as it breaks down, it will furnish valuable nutrients needed for plant growth. To increase the fertility of the forest garden ecosystem, nitrogen-fixing plants and plants can be added because they are grown specifically to provide some mulch. Forest gardens also include insect attracting plants to support beneficial insects that can reduce other pest populations without insect sprays and other chemicals.

Perennials are emphasized in forest gardens, because they reduce the need for annual starting and planting of seedlings. Those chores can then be eliminated. Designs may also include bird habitats for birds that spread seeds, provide fertilizer, and eat insects, toads that eat insects, and snakes that eat pests. Like natural forests, forest gardens are, to an extent, self-designing. The gardener may introduce more seeds and plants than will eventually survive. Only those that are well suited to the environmental conditions present in that place at that moment will thrive. In addition, a forest garden is designed to evolve over time. The plants that predominate at the beginning will likely fade away as others grow to take their places.

The plant list below provides a basic starting guideline and suggestions. Any plant that can grow in the surrounds of a forest garden can be included in that garden. This includes ornamental plants and even vegetables. In fact, many cool season vegetables will thrive in the shade and moisture of a forest garden. Summer vegetables can grow in a forest garden in its early years after it is first planted. On the other hand, they can be grown in sheet mulch on the garden's edge later on.


Shagbark Hickory
Sugar Maple
White Oak

American Persimmon
Cornelian Cherry
Kentucky Coffee Tree
Paw Paw
Witch Hazel

False indigo
Siberian Pea Shrub

Lemon balm
New Zealand Spinach
Salad burnet
Stinging Nettle


Hardy Kiwi
Scarlet Runner Bean


The best time to start a forest garden is in the fall, and trees and shrubs can be planted first. Plant trees and shrubs flush to, or just above ground level, then lay the sheet mulch on top of the ground around the plants. If trees and shrubs are not ready for planting at this time, just lay the sheet mulch and plant later.

The first step in preparing a sheet mulch is to "knock down" all unwanted vegetation. Knocking down is not pulling up or tilling under. You will use a lawn mower, weed whip, bush hog, scythe, pruning shears, or other implements to break off all the undesired plant life at, or just above, your ground level. If you have sod, leave it where it is and lay the sheet mulch atop it. Woody vegetation can be removed for chipping and become a pathway or part of the mulch later on. Thick woody roots will also need to be removed. They can be returned later for wildlife habitats. Otherwise, leave everything to decompose right where it is in order to fertilize your forest garden from the start

If the soil is compressed hard, break it up with a spading fork, a U-bar, or other similar implement. With the spading fork, insert the tines completely and lean on the handle. Break up the soil without turning it over. Now is the time to introduce soil boosters. A soil test will show whether it is necessary to adjust the soil pH with lime to increase its alkalinity or with sulphur to increase its acidity. This is important, so do not skip it. Then add any nutrients in which the soil was shown lacking. An inch or two of compost will add organic matter and nutrients to the soil and is the best general soil addition.

Next, add materials that are nitrogen-rich to draw worms up to help decomposition of the carbon-rich layers going on top. Composted manure is an excellent source, so add about 1 inch. Also use fresh vegetable scraps from home or from local restaruants. All of these enhancers or amendments are to be laid directly on top of the soil, one after the other, and not worked in at all. Just lay them out in layers.

Next in sequence is the light barrier. The object of this is to prevent the germination of weed seeds in the soil and to provide a physical barrier to weeds overall. Two materials good for this are newspaper and sheets of cardboard.

Remove any glossy color pages (metallic inks) from newspapers and remove tape and staples from the cardboard. Any solid total organic material is good, including old cotton clothing and rags. Lay newspaper and cardboard so that their edges overlap. The newspaper should be four sheets up to one half inch thick, depending on how many weeds you think you might get. Around tree trunks and shrubs, tear a section of newspaper or cardboard halfway through, and slide the edges of the tear around the trunk. Tear a second sheet in the same way and place it at right angles on top of the first tear. The light barrier is the key to the success of the sheet mulch, so take care with it. It takes some time to lay it, but it can save hours of weeding. Eventually, the newspaper and cardboard will all break down.

On top of the light barrier, place another layer of nitrogen-rich manure or vegetable scraps. Then lay up to 12 inches of bulk mulch. This mulch will consist of leaves, grass clippings, straw, wood chips, pine needles, branches, or any non-composted rough organic materials. The mulch can be placed in decisive layers, or mixed together. It need not be uniform, and leave some space around tree trunks and the bases of woody shrubs. Otherwise, rodents can come in to live in the mulch and nibble on the tree trunks.

If rodents are a probable problem, cut a slit in a metal can and place it, like a sleeve, around the base of the tree. Two considerations are important for the bulk mulch. One, avoid material that may contain seeds, such as hay and weeds. These materials can be included in a sheet mulch, but they should go beneath the light barrier. Two, creating a balance of carbon-rich browns and nitrogen-rich greens helps the mulch decompose. The ideal ratio of carbon to nitrogen is 30 to 1. Composting books are available, but an easy recipe is to mix fallen leaves with fresh grass clippings. If the crucial C to N balance has not been achieved, the mulch will still break down, but it will take longer. To facilitate this, use compost or manure teas (mixtures) as described below.

On top of the bulk mulch, one can place a final layer of hard mulch to make everything look tidy. This hard mulch could be straw, bark mulch, wood chips, or pine needles.

Allow the sheet mulch to compost for a period of time. If installed in the fall, it will partially break down over the winter. If it has been installed in the spring, it may only be possible to wait a few days or weeks before planting. Trees and larger shrubs should have been planted before the application of the sheet mulch but if not, remove a section of mulch, dig a hole, plant the tree, spread excess soil in the exposed area, and replace the mulch. The same applies to any large herbaceous plants. For transplants, plant with a trowel, a knife, and a bucket of topsoil or compost. With a knife, cut a slit or an X in the light barrier, insert the trowel into the slit, and dig a root pocket. Place the roots into the pocket and fill around them with topsoil or compost.

Return the mulch so the transplant is just sticking up through it. Large seeds, such as beans and squash, can be placed directly in the mulch if it is well decayed, or in slits in the light barrier. Fine seeds like those of carrots and lettuce can germinate on top soil or compost placed in the mulch. Clear the mulch aside from an area and cut holes or slits in the light barrier. Cover with top soil or compost. Sow the seeds and care for them as if they were in a bed in a traditional garden. In future years, plants such as dill and arugula may actually reseed themselves. This can be encouraged by placing a layer of compost around the plants as they begin to drop their seeds. The compost will trap the deeds for a new year and protect them from birds and animals.


The upkeep of a forest garden are the same as any other garden, but a well installed a forest garden will care for itself. Trees and shrubs in their first year may need some deep watering. Other plants should be watered when the soil beneath the light barrier dries out, or when the plants show signs of water stress. Deep mulch protects soils from wind and sun, so forest gardens require only occasional watering. Watering should entail a gentle flow from the garden hose, sprinklers, drip irrigation, soaker hoses, a watering wand, or a watering can.

If the sheet mulch is correctly installed, very few weeds will appear. Those few can be pulled and left on top of the mulch to dry, or placed underneath to rot.

Most nutrients needed in a forest garden will be provided by the decaying mulch. If a soil test reveals the need for specific nutrients, provide those at the time of the initial sheet mulching. Especially in its first year, a forest garden mulch may entrap nitrogen from the soil in its own process of decomposition.

The most important form of fertilization is to provide nitrogen to help the decomposition of the mulch and release nutrients to plants. The best way to provide this nitrogen is in liquid form as a "tea". This can be done by preparing a manure or compost tea and many recipes exist, requiring various levels of equipment and knowledge. A simple recipe is to fill a bucket or trashcan two-thirds full of manure or compost. Fill the container with water to a few inches below the edge. Cover with a sheet of plastic, tie it around the rim, and leave in the sun. Stir every day or two until the contents are smelly and bubbly - this should take about a week. Strain out the liquid, dilute at a concentration of 1 to 10, and water the whole garden with it. Plants in a forest garden can also be fertilized with a leaf application fertilizer.

Mulching is the most important single maintenance task and reduces the need for the watering, weeding, and fertilizing. This is even more important if your climate tends to be dry.

Any bare spots that appear in the mulch should be covered up with fresh material. If a large number of weeds breaks through in one area, remove the bulk mulch, add an additional layer of light barrier over the entire area, and replace the bulk mulch. If you are growing nitrogen fixing or mulch crops (Siberian pea shrub, comfrey), these can be cut back occasionally and either incorporated into a compost tea, or spread on the mulch surface to add nutrients. At the end of the season, spread several inches of leaves or other mulch material over the entire garden, and leave it to break down over the winter.

As a forest garden includes many perennial plants, clean up at the end of the season can be less of a task than in annual flower and vegetable gardens. Rather than pulling plants up, cut them off at ground level, which disturbs the soil less. The tops of the plants can then be incorporated into the mulch, or set aside for compost.

Planted forest gardens need dedicated human efforts in their beginning stages, but they can care for themselves for years after they develop into independent ecosystems. Forest gardens can provide food, flowers, and homes of wildlife, wind protection, cooling, and aesthetic pleasure in a variety of Midwest landscapes.

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